Contains information needed for generating an OAuth token
<https://developers.google.com/identity/protocols/OAuth2>__. This
type of authorization should generally only be used when calling
Google APIs hosted on *.googleapis.com.
.. attribute:: service_account_email
\ Service account email
<https://cloud.google.com/iam/docs/service-accounts>__ to be
used for generating OAuth token. The service account must be
within the same project as the job. The caller must have
iam.serviceAccounts.actAs permission for the service account.
